Precast concrete is a form of construction, where concrete is cast in a reusable mould or form which is then cured in a controlled environment. A precast sandwich panel (may also be referred to as double wall precast) may include two wythes (panels or layers) of reinforced concrete sandwiched around an insulating layer having a high R-value (a measure of thermal resistance). The insulation layer may be continuous throughout the wall section, and the two wythes of the interior and exterior concrete layers may be held together with trusses or ties.